Improving Thermoelectric Performance of AgSbTe2 through Suppression of Ag2Te and Band Convergence via Mg and Ti Codoping

Abstract

In this study, the impact of codoping Mg and Ti on the thermoelectric performance of AgSbTe₂ materials was investigated. Through a two-step synthesis process involving slow cooling and spark plasma sintering, AgSb_0.98-xMg_0.02Ti_xTe₂ samples were prepared. The introduction of Mg and Ti dopants effectively suppressed the formation of the undesirable Ag₂Te phase. Density functional theory (DFT) calculations confirmed that Ti doping facilitated the band convergence, leading to a reduction in the effective mass of the carriers. This optimization enhanced carrier mobility and, consequently, electrical conductivity. Additionally, the codoping strategy resulted in the reinforcement of point defects, which contributed to a decrease in lattice thermal conductivity. The AgSb_0.98-xMg_0.02Ti_xTe₂ sample achieved a maximum figure of merit (ZT) value of 1.45 at 523 K, representing an 87% improvement over the undoped AgSbTe₂ sample. The average ZT value over the temperature range of 323-573 K was 1.09, marking a significant enhancement in thermoelectric performance. This research demonstrates the potential of Mg and Ti codoping as a strategy to improve the thermoelectric properties of AgSbTe₂-based materials.

Keywords: Ag2Te secondary phase; AgSbTe2; Mg−Ti codoping; band convergence; thermoelectric performance.